Locking device for pressure fluid motors



July 18, 1950 AUDEMAR 2,515,287

LOCKING DEVICE FOR PRESSURE FLUID MOTORS Filed Sept. 7, 1945 2 Sheets-Sheet l EI EE AUDEMAK [N VE NT E. WQ MMMA *EW ATTHs.

July 18, 1950 P. AUDEMAR 2,515,287

LOCKING DEVICE FOR PRESSURE FLUID MOTORS Filed Sept. 7, 1945 2 Sheets-Sheet 2 C) PERRE {\UDEM R INVENTOFQ Patented July 18, 1950 LOCKING DEVICE FOR PRESSURE FLUID- [MOTORS f' PierreAudemar, La Garenne-Colombes', France, assignorv to. .Olaer Patent: :Cy, ,Luxemburg' (Duchy ofLuxernburg), a, company of Luxemburg, and Compagni e Generale pour IEquipe ment Aeronautique, Paris, Seine, France, a

v f company, of France Application September 7, 1945, Serial No. 615,050

In France December 18,1942

sectio 1, Public Law 690, August 8, 1946 Patent expires December 18, 1962' j 1 Claim. :(01. 121-40) The present invention relates tolocking devices for hydraulic jacks. and the like. i

The ,question is. of, considerable importance, especially in the case of. hydraulic jacks utilized in connection with airplane landing gears; In

this case, the locking must, on the onehand, be

absolutely safe, in order, for instance, to prevent lowering of the landing gear in flight, and, on the be easily understood that if, for anyreasonwhatever, the member to be locked tends to move before the locking part is fully retracted, it exerts thereon a violent thrust which produces jamming and tearing off of the metal of the locking member. I

On the other hand, when the meter to be locked, due to a temporary failing of the control device, does not get, during the retracting operation, its fully retracted position,- a locking piece of the kind that slides perpendicularly to the direction of movement of the member to be locked ment of the piston rod runs the risk of never getting into locking position and the device may remain unlocked without the pilot being aware of this.

The object of the present invention is to provide a device which avoids all these drawbacks and ensures a safe and elficient locking.

The locking device according to the present invention comprises, in combination with a hydraulic cylinder having a. piston movable therein and a piston rod for said piston, a lever pivoted to said cylinder about an axis perpendicular to the direction of sliding of said piston rod, said lever having a locking surface adapted to cooperate with a shoulder of said piston rod for holding it in locking position in which the locking surface is perpendicular to the longitudinal axis of said piston rod, the pivot of said lever being located substantially in the plane of said shoulder when said piston rod is in locking position, the circular arc described by each point of the outer end of said locking surface being tangential to the cylindrical surface of the piston rod at the begimiing of the unlocking movement, and means to maintain said lever in the locking position in which said lever is perpendicular to the longitudinal axis of said piston rod. The lever therefore follows, for part of its movement, the move- 56 2 to be locked, thus avoiding any risk of jamming and permits the parts to reach gradually locking position during the retracting movement of the piston rod to be locked, which piston rod is even pushed towardits locked position.- Other features of the invention will appear from the following description taken inconnection with the drawings forming a part of this specification, and in which: 1

Fig. 1 is an elevational view of a hydraulic jack :fit-ted with a locking device according 'to the invention, this jack being shown in its unlocked position.

Fig.12 is a vertical axial view of the jack of Fig; 1, shown in the locked position, and

Fig. 3 is a sectionmade ontheline 3-3 of Fig. 1. l

Referring to'the drawing, l is'the body of the jack and 2 the piston rod that slides inside this body. 'The jack is operated by a liquid under pressure, such for instance as oil, fed through a conduit 3 for expansion of the jack and through a conduit I3 for its retraction. The locking device'is constituted by a lever 5 which forms the locking'piece proper and a toggle 4-6. The end 5bof lever 5 has a locking surface 5a adapted to cooperate with a shoulder 2a on piston rod 2.

Lever 6 pivots about a fixed axis 8 and lever'5 about afixed axis 1 in such a manner that its end 5b describes, during locking'and unlocking movement, a circular are which is tangential to the cylindrical surface of piston rodZ. The ends ofvlevers5 and 6 are connected together by a link 4 pivoted at 9 and I II to levers 5 and 6, respec- ,tively.= A spring I2 is-interposed between a fixed point l4 of the jack and a point I l of lever 6. Control of the toggle is ensured through a small piston l5 actuated by oil under pressure fed through conduit I6.

Operation of this device takes place as follows:

In the locking position shown by Fig. 2, the lever 5 abuts with its locking surface 5a against the shoulder 2a of piston rod 2, said locking surface being perpendicular to the longitudinal axis of said piston rod, and the pivot point In of link 4 is located on a line passing through axis 8 of lever 6 and pivot 9 of link 4 or slightly above this line. Under these conditions, any action tending to produce expansion of the jack, that is to say to move lever 5 in a counterclockwise direction, is impossible. In order to start the movement of lever 5 in this direction, it is necessary first to bring pivot point l0 below this line of axis 8 and pivot 9, and as a matter of tact the efforts that would tend to produce expansion of the jack tend to push this pivot 10 in the-opv posite direction, that is to say above the said line. The jack is therefore perfectly well looked.

n the other hand, spring 12. also tends to keep pivot l0 on--or slightly above-the line passing through the axis 8 and pivot 9.

Unlocking can take place only when :liqauid 11nder pressure is fed through pipe-4 6 170 thesmal'l piston 15. V

The liquid under pressure fed-through conduit- 3 opens check valve l1 and passes through orifice l8 into the cylinder l of the jack. This liquid pipe I6 and pushes to the right piston 15' which acts on the lever 6 0f the toggle. 'I'he-v latter is then broken, that is to say pivot'poinlt Hl' is brought below the line passing through axis 8 under pressure then passes throughori'fice lzllinto and pivot 9. Simultaneously, piston rod 2 starts moving toward the rightand the end 52) of lever 5,. which constitutes; the locking piece proper, follows, for-part of its movement; this movement ofthe-pistonrod.

In order to retract rod2;, liquid underpressure tion of Fig. 1 during, thewhole retracting of the jack. For this purpose, the liquid present in-lcyl! inder I, on ,the'left hand side of piston I9, is compelled, in order to escape through conduit ,to-

raise a valve constituted by a ball 2| subjected to the action of a spring 22-, which therefcre prod-uces a counter-pressure in the liquid in question.

This counter-pressure is transmitted" to the liquid present in pipe l6 and it pushes tothe right piston so as tokeep'the toggle inthe positionof, Fig. 1-. It is only at the end of. the

stroke of piston l9, that. a push-piece 23 pro.- vided at the center of this piston, enters orifice 26v and pushes back checkva-lve 2| so as'to permit the liquid present in pipe .I G-to flow outwith;- out: counter-pressure. Rod 2 is now fully: re

tractedand spring l2 causes locking to take place by bringing the toggle into the position or Fig; 2..

It is thereforeclear that the locking deviceaccording to-theinvention never moves perpendicularly tothe direction of displacement or'theomemhero to be lockedas long asit is incontact. there- In order to with, which avoids anypossibility'of jamming. On the other hand, at thetime of the retraction of the member to be locked, it accompanies the movement of the latter and exerts a thrust in the direction of its retraction.

Ina general'manner, while I have, in the above description, disclosed what I deem to be practical and efiicient embodiments of the present invention, it should be well understood that I do not -wish t0- belimited thereto as there might be changes made in "the arrangement, disposition and form of'the parts without departing from the principle of the present invention as comprehended within the scope of the appended claim;

Whatl claimis:

'A locking device comprising, in combination with a hydraulic cylinder, a piston movable therein anda piston rod for said piston, a lever pivoted to said cylinder about an axis perpendicular to the direction of sliding. of said piston rod, a shoulder provided on said-1 piston rod, the pivot of said :lever beingl located substantially in the plane of said shoulderwhen:said piston rod is in lockingposition, saidlever having a locking surface adapted-to cooper-ate with said shoulder for holdingsaid pistonrodzin lockingpositionin which saidlocking surface is perpendicular to the longi-tudinal axis of; said pistonrod the circular arc described by each point: of the outer end of said locking, surface: beingatangential to the cylindrical surface of said piston rod atthebeginning 0f the unlocking movement, av toggle-joint interposed between said cylinder" and saidlever for locking thev latter ink-locking iposition, hydraulic motor means for bringing: said. toggle joint beyond the positionin which saidlever is released, a fluid connection between said cylinder and said hydraulic motor meansg-and a valve-arrangementin said fluid: connection operative to build up pressure in: the connection: at the initial stage of the extension and also during retraction of said piston rod.

PIERRE AUDEMAR.

REFERENCES CITED The following references are of recordin the file. of. this patent:

UNITED: STATES PATENTS Number Name Date 1,038,813? Brinc'kerhofi" Sept. 17, 1912. 1,583,189 Scott" May 4, 1926 1,694,980" Pearmain Dec. 11, 1928' 

